The invention generally relates to a rolling mill for producing plate and strip, and in particular to a rolling mill in which two-dimensional central support is automatically formed so as to control the roll""s flexure, thereby the rolled plate and strip have very high thickness precision in cross section.
Generally, there are a variety of kinds of rolling mills for rolling plate and strip, and they are classified according to the number of rolls into the two-high mill, the four-high mill and the cluster mill, but the most commonly used rolling mills are the four-high mill, the HC mill and the cluster mill and so on. For two-high type, four-high type mills, there exist many disadvantages, the main disadvantage is that: when a piece to be rolled passes the mill stand, since the downward driving devices are located at the necks of the rolls, the rolls are caused to have larger bending deformation, and the deformations of the rolls will result in the thickness error in the cross section of the rolled piece (rolled plate and strip), thus seriously affecting the quality of the rolled piece. To solve the above problem, the method of increasing the diameter of the rolls has to be adopted, and for a four-high mill, also the method of increasing the diameter of the supporting rolls has to be adopted. However, as the diameter of the rolls increases, it is certain to cause the rolling forces to abruptly increase, and the increase of the rolling forces in turn causes an increase of the bending deformation of the rolls.
The cluster mills include integral housing type mills and open type mills (as shown in FIGS. 1, 2), Japanese Patent 54-1259 discloses a cluster mill which adopts a tower-like roll system. Of course, such rolling mills all have the advantage of high rigidity, but in a cluster mill, the portions of the mill frame which contact the supporting rolls still have bending deformation under rolling forces, thus causing the flexural deformation of the working rolls and affecting the uniformity of the thickness of rolled piece as a result.
The solution to the problem of the roll""s flexural deformation to reduce or eliminate the effect of the roll""s flexural deformation on the thickness of rolled piece consists in the control of the shape of the clearance between the working rolls to make the flexural deformation of the working rolls not to be affected by the change of rolling forces. A Chinese Patent (application number 89101393, issue number CN 1013250B) discloses xe2x80x9cA rolling mill with rolls of small flexure and high rigidityxe2x80x9d. To achieve above object, according to the patent, the supporting rolls at the outermost layer of the tower-like roll system are supported on the roll supports in the form of a mufti-section beam; rolling forces acting on the working rolls are transmitted respectively to the upper and lower roll supports via the roll systems; the vertical component of the force borne by the roll supports are transmitted to the mill frame via the downward driving or upward driving devices or similar elements such as pads; the number of the downward driving or upward driving devices is at least two, and the positions of the downward driving or upward driving devices are in the middle region of the axis of the working roll on the roll supports. It can be seen, the solution of that patent can make the flexural deformation of the roll supports in the vertical plane not vary with the rolling forces in the main, thus effectively reducing the thickness error in the cross-section of the rolled piece. However, for the cluster mills with tower-like roll systems, the force transmitted from the working rolls to the intermediate rolls has vertical and horizontal components, therefore the peripheral supporting rolls also bear significant horizontal component force. For the rolling mill disclosed in Chinese Patent 89101393, the horizontal component force causes the roll supports to have horizontal flexural deformation, thus causing the axis of the supporting rolls, the intermediate rolls and even the working rolls to have larger flexural deformation.
As stated above, to solve the problem of flexural deformation of the working rolls of a cluster mill, it is not only necessary to reduce the flexural deformation produced by the vertical component force, but also that produced by the horizontal component force, that is, it is obliged to solve the problem of deformation in two-dimensional directions, so that a working roll can be held straight and the thickness precision in the cross-section of the rolled piece can be increased.
Therefore, the invention is aimed to solve the problem of the two-dimensional flexural deformation of the rolls, namely, the rolling mill of the invention can reduce not only the flexural deformation in vertical direction, but also that in horizontal direction. Accordingly, the object of the invention is to provide a high-precision rolling mill, as compared with the prior art, when the rolling mill of the invention is subjected to the rolling force, the flexural deformation of the rolls can be greatly reduced, resulting in the reduction of the thickness error in the cross-section of the rolled piece and the increase of the dimension accuracy of the rolled piece.
To achieve the above-mentioned object, there is provided a rolling mill for rolling plate and strip comprising: a mill frame; an upper roll system and a lower roll system; and an upper middle roll support, an upper lateral roll support, a lower middle roll support and a lower lateral roll support. The mill frame is of a frame type and is able to bear rolling forces, and all parts and components of the rolling mill, such as the roll systems, are incorporated in the frame. The roll systems are so arranged as to be of a tower-like configuration. The roll system is composed of three parts, a working roll, supporting rolls and intermediate rolls; the upper and lower supporting rolls disposed at the outermost layer of the roll system are respectively supported on the upper and lower middle roll supports and the upper and lower lateral roll supports in the form of a mufti-section beam, and the upper middle roll support and the upper lateral roll support can be moved up and down if necessary to adjust the magnitude of the clearance between the rolls. The mill frame, the roll supports, the central supporting means between the middle roll supports and the lateral roll supports, the central supporting means between the frame and the middle roll supports and the central supporting means between the frame and the lateral roll supports commonly form a two-dimensional central supporting system. The lateral roll supports automatically press tightly against the side walls of the frame under the action of horizontal component force. The central supporting means is disposed on at least one of the upper and lower roll supports, and is arranged in the region near the middle part of the roll body axis of the working roll with its length being not longer than the length of the roll body of the working roll. The central supporting means includes driving devices and horizontal pads; there are at least two driving devices disposed above the upper middle roll support and placed in the mill frame, the lower middle roll support is supported by horizontal pads. Both the driving devices and the horizontal pads are arranged in the region near the middle part of the roll body axis of the working roll. In the rolling mill of invention, there are also disposed upper and lower vertical pads along a horizontal direction, which are respectively positioned between the side surfaces of the upper and lower lateral roll supports and the mill frame. Under the action of horizontal component force, the lateral roll supports press tightly against the side walls of the mill through the vertical pads, thus being centrally supported in the horizontal direction so as to prevent flexural deformation due to horizontal component force. In the rolling mill of the invention, horizontal pads are disposed between the middle roll supports and the lateral roll support to further provide central support to the lateral roll supports in the vertical direction. The shape of the mill frame is mated with that of the combined roll supports.